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From: mk59200@metso.tut.fi (Kolkka Markku Olavi)
Newsgroups: comp.dcom.telecom
Subject: Re: IRIDIUM: Motorola's New Cellular Phone System
Message-ID: <10645@accuvax.nwu.edu>
Date: 9 Aug 90 10:33:42 GMT
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X-Telecom-Digest: Volume 10, Issue 553, Message 9 of 11


In article <10597@accuvax.nwu.edu>, cfogg@milton.u.washington.edu (Chad
Fogg) writes:

|> >	The system is designed as an entirely digital communications
|> >system with 8KHz bandwidth available for each voice channel. Vocoders

|> Is this 8KHz sample rate or 8KHz frequency bandwidth?

It looks like it is 8kHz bandwith (>16kHz sampling), with quite a lot
of data compression to reduce the data rate.

|> >operating at 4.8 kilobits per second are employed in the user units to
                 ^^^^^^^^^^^^^^^^^^^^^^^
|> >	The system is designed to allow a user to substitute a data
|> >link in lieu of a voice link which would operate at a rate of 2400
|> >baud.

|> 2400 bps is kind of a dissapointment when the voice channel is
|> operating at 64,000 bps.

But the document tells us the voice channel is 4800bps.  Data
transmission needs additional error correction and detection which
reduces the speed.

Does anybody know what kind of compression they plan to use to squash
8kHz bandwith sound through a 4800bps channel?


Markku Kolkka
mk59200@tut.fi